A method for plasma-enhanced chemical vapor deposition, by which a substance such as a semiconductor, for example, is vapor deposited on a substrate, has hitherto been carried out as follows using an apparatus for plasma-enhanced chemical vapor deposition having a vacuum film formation chamber.
This apparatus for plasma-enhanced chemical vapor deposition is provided with a substrate disposed in a vacuum atmosphere, a ground electrode which holds the substrate and is grounded, and a ladder-shaped electrode which is disposed in parallel with and opposite to the substrate at a distance. Plasma is generated between the ladder-shaped electrode and the substrate by introducing a gas for forming a film containing the aforesaid substance into this apparatus for plasma-enhanced chemical vapor deposition, and by feeding the ladder-shaped electrode with electric power from a high-frequency electric power feeding circuit. Then, the gas for forming a film is decomposed in the plasma, and the substance is vapor deposited on the substrate (for example, see Japanese Patent Application, First Publication (Kokai), No. 2001-274099).
When a film is formed on a substrate having a large area exceeding, for example, the dimensions (length by breath) of 1 m by 1 m using an apparatus for plasma-enhanced chemical vapor deposition as described above, in order to make the distribution of the thickness of the film, which is formed in the vacuum film formation chamber, uniform over the entirety of the substrate, measures are taken that makes the distribution of the voltage of a high-frequency electric power supply, which is applied between the ladder-shaped electrode and the substrate so as to generate plasma, uniform over the entirety of the substrate. For example, as disclosed in the above patent document, two streams of high-frequency electric power, which have the same frequency, but a difference in phase between one stream of high-frequency electric power and the other stream of high-frequency electric power, are generated by a high-frequency electric power feeding circuit, and are distributed to discharge electrodes which constitute the ladder-shaped electrode via a plurality of cables. Accordingly, generation of standing waves on the discharge electrodes, which inhibit provision of uniformity in the film thickness, is avoided, and the high-frequency electric power generated by the high-frequency electric power feeding circuit is stably supplied.